Preparation method of functionalized bacterial cellulose cross-linked composite basic polyelectrolyte membrane

Abstract

The application relates to the technical field of fuel cells, and particularly discloses a preparation method of a functionalized bacterial cellulose crosslinked composite alkaline polyelectrolyte membrane. The preparation method comprises the following steps: 1) performing purification treatment on bacterial cellulose; 2) performing quaternary ammonium-tertiary amine functionalization modification on the purified bacterial cellulose; 3) dissolving brominated polyphenyl ether and impregnating and filling the brominated polyphenyl ether into the pores of the quaternary ammonium-tertiary amine functionalized bacterial cellulose to perform crosslinking reaction with the functionalized bacterial cellulose; and 4) quaternary ammoniating the residual brominated polyphenyl ether solution after impregnation and crosslinking, and the functionalized bacterial cellulose is obtained. The bacterial cellulose which is modified through a series of chemical modifications is used as a substrate, and the quaternary ammoniated polyphenyl ether is used as a filler. The interface combination of the substrate and the quaternary ammoniated polyphenyl ether is enhanced, mechanical reliability is ensured, the inert substrate is endowed with certain ion transmission capacity, the composite ion exchange membrane reaches a balance in ion conductivity, mechanical performance and alkaline stability and the like, and certain use benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and specifically to a method for preparing a functionalized bacterial cellulose crosslinked composite alkaline polyelectrolyte membrane. Background Technology

[0002] A fuel cell is a chemical device that directly converts the chemical energy of fuel (hydrogen / methanol, oxygen) into electrical energy. Also known as an electrochemical generator, it represents a new generation of power generation technology. Its power generation process requires no mechanical transmission, thus it is not limited by the Carnot cycle effect, resulting in high efficiency and low noise. Furthermore, its fuel is single and clean, emitting very few harmful gases. It is also very convenient to use; unlike rechargeable batteries such as lithium batteries, fuel cells only require refueling and can continuously generate electricity without needing to be recharged.

[0003] Alkaline anion exchange membrane fuel cells (AEMFCs), which do not rely on precious metal catalysts and exhibit faster oxygen reduction reaction kinetics, have become a new research hotspot in this field. The anion exchange membrane is the core component of the AEMFC, playing a crucial role in conducting OH-... - In addition to their dual function of separating fuel and oxidant, high-performance alkaline anion exchange membranes should simultaneously possess high ionic conductivity and chemical and mechanical stability. However, there are currently no commercially available anion exchange membranes whose comprehensive performance fully meets the requirements for battery use. Therefore, designing a high-performance alkaline polyelectrolyte that combines high ionic conductivity, mechanical strength, and good chemical stability is the primary task of AEMFC technology. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a (crosslinked) composite alkaline polyelectrolyte membrane using bacterial cellulose or functionalized bacterial cellulose porous material as a substrate by filling with quaternized polyphenylene ether.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] Option 1: Using bacterial cellulose as a substrate

[0007] A method for preparing a bacterial cellulose composite alkaline polyelectrolyte membrane includes the following steps:

[0008] (1) Purification treatment of bacterial cellulose membrane;

[0009] (2) Dissolve brominated polyphenylene ether and impregnate it into the pores of the purified bacterial cellulose membrane obtained in step (1) to obtain a polymer-filled bacterial cellulose membrane;

[0010] (3) Quaternize the brominated polyphenylene ether solution in the bacterial cellulose membrane filled with the polymer obtained in step (2), impregnate the bacterial cellulose membrane, and then dry and ion exchange to obtain a bacterial cellulose composite alkaline polyelectrolyte membrane.

[0011] Further, in step (1), the purification process is as follows: the bacterial cellulose membrane is soaked in deionized water for 12-48 hours to allow it to fully swell, then taken out and soaked in a 0.1-1 mol / L NaOH solution and heated at 80-90°C for 2-3 hours, then cooled to room temperature, and then repeatedly washed with a large amount of deionized water until neutral to obtain the purified bacterial cellulose membrane; further, the bacterial cellulose has a diameter of 30-100 nm and a length of 10 μm-50 μm; preferably, the bacterial cellulose has a diameter of 50-100 nm and a length of 10 μm-20 μm.

[0012] Further, in step (2), the brominated polyphenylene ether is dissolved to form a brominated polyphenylene ether solution with a concentration of 1wt% to 5wt%, wherein the degree of bromine substitution of the brominated polyphenylene ether is 40% to 60%; the solvent for dissolving the brominated polyphenylene ether is selected from any one of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0013] Furthermore, in step (2), the soaking time is preferably 12 to 24 hours.

[0014] Furthermore, in step (3), the quaternizing agent is trimethylamine, preferably an alcoholic solution of trimethylamine, such as a 33wt% trimethylamine methanol solution; the quaternization time is 12-24h.

[0015] Furthermore, in order to enhance the compatibility between bacterial cellulose and the filler brominated polyphenylene ether, the bacterial cellulose was functionalized to prepare a functionalized bacterial cellulose crosslinked composite alkaline polyelectrolyte membrane.

[0016] Option 2: Using functionalized bacterial cellulose porous materials as a substrate

[0017] A method for preparing a functionalized bacterial cellulose crosslinked composite alkaline polyelectrolyte membrane includes the following steps:

[0018] (1) Purification treatment of bacterial cellulose membrane;

[0019] (2-1) The purified bacterial cellulose membrane was functionalized with quaternary ammonium-tertiary amine to obtain a functionalized bacterial cellulose porous substrate.

[0020] (2-2) Dissolve brominated polyphenylene ether and impregnate it into the pores of the functionalized bacterial cellulose porous substrate obtained in step (2-1). The brominated polyphenylene ether undergoes a cross-linking reaction with the functionalized bacterial cellulose porous substrate to obtain a polymer cross-linked functionalized bacterial cellulose membrane.

[0021] (3) Quaternize the brominated polyphenylene ether solution that has been impregnated with the crosslinking residue in the polymer crosslinked functionalized bacterial cellulose membrane obtained in step (2-2), impregnate and fill the bacterial cellulose, and then dry and ion exchange to obtain a functionalized bacterial cellulose crosslinked composite alkaline polyelectrolyte membrane.

[0022] Further, in step (1), the purification process is as follows: the bacterial cellulose membrane is soaked in deionized water for 12-48 hours to allow it to fully swell, then taken out and soaked in a 0.1-1 mol / L NaOH solution and heated at 80-90°C for 2-3 hours, then cooled to room temperature, and then repeatedly washed with a large amount of deionized water until neutral to obtain the purified bacterial cellulose membrane; further, the bacterial cellulose has a diameter of 30-100 nm and a length of 10 μm-50 μm; preferably, the bacterial cellulose has a diameter of 50-100 nm and a length of 10 μm-20 μm.

[0023] Furthermore, the step (2-1) of functionalizing the quaternary ammonium-tertiary amine is as follows:

[0024] S1. The purified bacterial cellulose was first immersed in a Tris buffer solution containing dopamine hydrochloride at pH 8 to 8.5, and after sonication, the mixture was stirred for 12 to 24 hours to obtain a polydopamine-coated bacterial cellulose membrane.

[0025] S2. The polydopamine-coated bacterial cellulose membrane obtained in step S1 is immersed in a Tris buffer solution containing polyethyleneimine, ultrasonically treated, and then impregnated for 24 to 48 hours to obtain a polydopamine-polyethyleneimine-coated bacterial cellulose membrane.

[0026] S3. The polydopamine-polyethyleneimine-coated bacterial cellulose membrane obtained in step S2 is immersed in a 2,3-epoxypropylammonium chloride solution, ultrasonically treated, stirred at room temperature for 1 to 3 hours, and then treated at 70 to 80°C for 4 to 6 hours to obtain a functionalized bacterial cellulose porous substrate.

[0027] Further, in step S1, the mass concentration of dopamine hydrochloride is 1-5 g / L; in step S2, the mass concentration of polyethyleneimine is 2-12 g / L, preferably 6-8 g / L, more preferably 8 g / L; in step S2, the average molecular weight of polyethyleneimine is 10,000-50,000; in steps S1 and S2, the Tris buffer solution is an aqueous solution of tris(hydroxymethyl)aminomethane, wherein the molar concentration of tris(hydroxymethyl)aminomethane is 0.01-0.04 mol / L; in step S3, the mass concentration of 2,3-epoxypropylammonium chloride is 3-4 g / L, preferably 3.33 g / L.

[0028] Furthermore, the ultrasonic treatment steps in steps S1, S2, and S3 are as follows: set the ultrasonic frequency to 40 kHz, the power to 200 W, and perform ultrasonic treatment for 5 minutes.

[0029] Furthermore, steps S1, S2, and S3 may also include a post-processing step, in which the obtained product is repeatedly washed with deionized water to remove impurities.

[0030] Further, in step (2-2), the brominated polyphenylene ether is dissolved to form a brominated polyphenylene ether solution with a concentration of 1wt% to 5wt%, wherein the degree of bromine substitution of the brominated polyphenylene ether is 40% to 60%; the solvent for dissolving the brominated polyphenylene ether is selected from any one of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0031] Furthermore, in step (2-2), the soaking time is preferably 12 to 24 hours.

[0032] Furthermore, in step (3), the quaternizing agent is trimethylamine, preferably an alcoholic solution of trimethylamine, such as a 33wt% trimethylamine ethanol solution; the quaternization time is 12-24h.

[0033] The application of the bacterial cellulose composite alkaline polyelectrolyte membrane and the functionalized bacterial cellulose cross-linked composite alkaline polyelectrolyte membrane prepared by the above method in the preparation of anion exchange membrane fuel cells.

[0034] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0035] (1) The composite alkaline polyelectrolyte membrane prepared by the present invention using bacterial cellulose as a substrate and filling quaternized polyphenylene ether has excellent ionic conductivity, mechanical properties and alkaline stability.

[0036] (2) The present invention performs a series of chemical modifications on bacterial cellulose before filling it with quaternized polyphenylene ether, which increases the compatibility with quaternized polyphenylene ether filler. At the same time, chemical crosslinking also makes the internal structure of the composite membrane more compact, ensuring the mechanical reliability and interfacial bonding of the composite membrane. Attached Figure Description

[0037] Figure 1 Fourier transform infrared spectra of the films prepared in Comparative Example 1, Example 1, and Example 4.

[0038] Figure 2 The images shown are scanning electron microscope (SEM) images of the purified bacterial cellulose used in Examples 2, 3, 4, and 5.

[0039] Figure 3 This is a scanning electron microscope image of the bacterial cellulose / quaternized polyphenylene ether composite alkaline polyelectrolyte membrane prepared in Example 1.

[0040] Figure 4This is a scanning electron microscope image of the functionalized bacterial cellulose / quaternized polyphenylene ether crosslinked composite alkaline polyelectrolyte membrane prepared in Example 2.

[0041] Figure 5 This is a scanning electron microscope image of the functionalized bacterial cellulose / quaternized polyphenylene ether crosslinked composite alkaline polyelectrolyte membrane prepared in Example 3.

[0042] Figure 6 The images are scanning electron microscope (SEM) images at different magnifications of the functionalized bacterial cellulose / quaternized polyphenylene ether crosslinked composite alkaline polyelectrolyte membrane prepared in Example 4.

[0043] Figure 7 This is a scanning electron microscope image of the functionalized bacterial cellulose / quaternized polyphenylene ether crosslinked composite alkaline polyelectrolyte membrane prepared in Example 5. Detailed Implementation

[0044] The applicant will now provide a more detailed description of the technical solution of the present invention in conjunction with specific embodiments, with the aim of enabling those skilled in the art to have a clearer understanding and knowledge of the present application.

[0045] The following specific embodiments should not be construed or interpreted in any way as limiting the scope of protection claimed in this application.

[0046] The bacterial cellulose membranes used in the following examples were purchased from Guilin Qihong Technology Co., Ltd., brand name BC. The bacterial cellulose had a diameter of 50-100 nm and a length of 10 μm-20 μm.

[0047] The brominated polyphenylene ether used in the following examples was prepared as follows: 8 g of polyphenylene ether was dissolved in 160 mL of chlorobenzene and stirred for 30 min. Then, 4.15 g of N-bromosuccinimide and 0.182 g of azobisisobutyronitrile were added. After one hour, N-bromosuccinimide and azobisisobutyronitrile were added again in the same amounts, repeated three times in total. The entire reaction was carried out at 80 °C under an inert atmosphere. After the reaction was completed, the resulting mixture was poured into methanol to precipitate the polymer. The mixture was filtered, and the precipitate was washed three times with methanol. Then, it was dried in a vacuum oven at 60 °C for 24 hours to obtain the brominated polyphenylene ether. The degree of bromination was calculated to be 40% by 1H NMR spectroscopy.

[0048] The average molecular weight of the polyethyleneimine used in the following examples is 10,000.

[0049] The Tris buffer solution used in the following examples is an aqueous solution of tris(hydroxymethyl)aminomethane, wherein the molar concentration of tris(hydroxymethyl)aminomethane is 0.01 mol / L.

[0050] Example 1: A method for preparing a bacterial cellulose / quaternized polyphenylene ether composite alkaline polyelectrolyte membrane, comprising the following steps:

[0051] (1) The bacterial cellulose membrane (about 9×9cm) was soaked in deionized water for 48h to allow it to fully absorb water. After taking it out, it was soaked in 0.1mol / L NaOH solution and heated at 80℃ for 3h. Then it was cooled to room temperature and repeatedly washed with a large amount of deionized water. The pH value was tested by lightly pressing the membrane surface with pH test paper. When the pH value was neutral (pH=7), it was freeze-dried using a freeze dryer at -60℃ for 24h to obtain the bacterial cellulose membrane.

[0052] (2) Dissolve brominated polyphenylene ether (bromine substitution degree of 40%) in N-methylpyrrolidone to form a polymer solution with a mass concentration of 1 wt%.

[0053] (3) Immerse the bacterial cellulose membrane obtained in step (1) into the polymer solution obtained in step (2), crosslink at room temperature and stand for 24 hours to obtain a polymer-filled bacterial cellulose membrane.

[0054] (4) Add 4 mL of 33 wt% trimethylamine ethanol solution to the polymer-filled bacterial cellulose membrane obtained in step (3) for quaternization, impregnate and fill at room temperature for 24 hours, and then dry at 50°C for 24 hours to obtain a dry membrane. Then immerse the dry membrane in 3 mol / L NaOH solution for anion exchange for 24 hours to obtain a bacterial cellulose / quaternized polyphenylene ether composite alkaline polyelectrolyte membrane.

[0055] Example 2: A method for preparing a functionalized bacterial cellulose / quaternized polyphenylene ether crosslinked composite alkaline polyelectrolyte membrane, comprising the following steps:

[0056] (1) The bacterial cellulose membrane (approximately 9 × 9 cm) was soaked in deionized water for 48 hours to allow it to fully absorb water. After removal, it was soaked in 0.1 mol / L NaOH solution and heated at 80°C for 3 hours. Then, it was cooled to room temperature and repeatedly washed with a large amount of deionized water. The pH value was tested by gently pressing the membrane surface with pH paper. When the pH value was neutral (pH = 7), the purified bacterial cellulose was obtained. Its scanning electron microscope image is shown below. Figure 2 ;

[0057] (2) The purified bacterial cellulose obtained in step (1) was immersed in 100 mL of Tris buffer solution containing 0.1 g dopamine hydrochloride. The ultrasonic frequency was set to 40 kHz and the power to 200 W. The ultrasonic treatment was carried out for 5 min. Then the reaction was stirred at room temperature for 12 hours. The membrane was taken out and washed repeatedly with deionized water to remove unreacted dopamine hydrochloride and polydopamine that did not coat the bacterial cellulose. After washing, the bacterial cellulose coated with polydopamine was obtained.

[0058] (3) Immerse the polydopamine-coated bacterial cellulose obtained in step (2) in 50 mL of Tris buffer solution containing 0.1 g polyethyleneimine, set the ultrasonic frequency to 40 kHz and the power to 200 W, ultrasonically treat for 5 min, and then immerse at room temperature for 48 hours. Take out the membrane and wash it repeatedly with deionized water to remove unreacted polyethyleneimine. After washing, polydopamine-polyethyleneimine-coated bacterial cellulose is obtained.

[0059] (4) The polydopamine-polyethyleneimine-coated bacterial cellulose obtained in step (3) was immersed in a 3.33 g / L 2,3-epoxypropyltrimethylammonium chloride solution. The ultrasonic frequency was set to 40 kHz and the power to 200 W. The ultrasonic treatment was performed for 5 min. The membrane was first stirred at room temperature for 3 hours and then treated at 70 °C for 6 hours. The membrane was then removed and repeatedly washed with deionized water to remove unreacted 2,3-epoxypropylammonium chloride. Then, it was freeze-dried using a freeze dryer at a cold trap temperature of -60 °C for 24 h to obtain a functionalized bacterial cellulose porous substrate.

[0060] (5) Dissolve brominated polyphenylene ether (bromine substitution degree of 40%) in N-methylpyrrolidone to form a polymer solution with a mass concentration of 1 wt%.

[0061] (6) Immerse the functionalized bacterial cellulose porous substrate obtained in step (4) into the polymer solution obtained in step (5), crosslink at room temperature and stand for 24 hours to obtain a polymer crosslinked functionalized bacterial cellulose membrane.

[0062] (7) Add 4 mL of 33 wt% trimethylamine ethanol solution to the polymer cross-linked functionalized bacterial cellulose membrane obtained in step (6) for quaternization, impregnate and fill at room temperature for 24 hours, and then dry at 50°C for 24 hours to obtain a dry membrane. Then immerse the dry membrane in 3 mol / L NaOH solution for anion exchange for 24 hours to obtain a functionalized bacterial cellulose / quaternized polyphenylene ether cross-linked composite alkaline polyelectrolyte membrane.

[0063] Example 3: A method for preparing a functionalized bacterial cellulose / quaternized polyphenylene ether crosslinked composite alkaline polyelectrolyte membrane

[0064] The preparation method of this embodiment is the same as that of Example 2. The only difference is that in step (3), the polydopamine-coated bacterial cellulose membrane obtained in step (2) is immersed in 50 mL of Tris buffer solution containing 0.2 g of polyethyleneimine.

[0065] Example 4: A method for preparing a functionalized bacterial cellulose / quaternized polyphenylene ether crosslinked composite alkaline polyelectrolyte membrane

[0066] The preparation method of this embodiment is the same as that of Example 2. The only difference is that in step (3), the polydopamine-coated bacterial cellulose membrane obtained in step (2) is immersed in 50 mL of Tris buffer solution containing 0.4 g of polyethyleneimine.

[0067] Example 5: A method for preparing a functionalized bacterial cellulose / quaternized polyphenylene ether crosslinked composite alkaline polyelectrolyte membrane

[0068] The preparation method of this embodiment is the same as that of Example 2. The only difference is that in step (3), the polydopamine-coated bacterial cellulose membrane obtained in step (2) is immersed in 50 mL of Tris buffer solution containing 0.6 g of polyethyleneimine.

[0069] Comparative Example 1: A method for preparing a quaternized polyphenylene ether alkaline polyelectrolyte membrane, comprising the following steps:

[0070] (1) Dissolve brominated polyphenylene ether (bromine substitution degree of 40%) in N-methylpyrrolidone to form a polymer solution with a mass concentration of 1 wt%;

[0071] (2) Add 4 mL of 33 wt% trimethylamine alcohol solution to the polymer solution obtained in step (1) for quaternization. Quaternize at room temperature for 24 hours. Then spread the solution on a glass plate and dry at 50°C for 24 hours to obtain a dry film. Then immerse the dry film in 3 mol / L NaOH solution for anion exchange for 24 hours to obtain a quaternized polyphenylene ether alkaline polyelectrolyte membrane.

[0072] Figure 1 The Fourier transform infrared (FTIR) spectra of the films prepared in Comparative Example 1, Example 1, and Example 4 are shown. In the FTIR spectra, the stretching vibration peak of OH is at 3342 cm⁻¹. -1 The PDA ring vibration peak was observed in bacterial cellulose, dopamine-coated bacterial cellulose, functionalized bacterial cellulose, bacterial cellulose / quaternized polyphenylene ether, and functionalized bacterial cellulose / quaternized polyphenylene ether. For dopamine-coated bacterial cellulose and functionalized bacterial cellulose, the PDA ring vibration peak was observed at 1648 cm⁻¹. -1 and 1508cm -1 Location. 1454cm -1 The -CH2 bending vibration peak at 1600 cm⁻¹ confirmed the grafting process of polyethyleneimine. Functionalized bacterial cellulose was successfully prepared through multiple impregnation treatments. -1 and 1189cm -1 The signals at 1460 cm⁻¹ represent the tensile vibration peaks of C=C in the aromatic ring of polyphenylene ether and COC on the main chain, respectively. -1The peak at this location may originate from the bending vibration of -CH2 between the polyphenylene ether and quaternary ammonium groups. Characteristic peaks of quaternized polyphenylene ether are observed in both bacterial cellulose / quaternized polyphenylene ether and functionalized bacterial cellulose / quaternized polyphenylene ether, thus demonstrating the feasibility of preparing functionalized bacterial cellulose / quaternized polyphenylene ether composite membranes.

[0073] The performance test results of the membranes prepared in Examples 1 to 5 and Comparative Example 1 are shown in Table 1.

[0074] Table 1. Performance test results of the membranes prepared in Examples 1-5 and Comparative Example 1

[0075]

[0076] As shown in Table 1, the cross-linked composite alkaline polyelectrolyte membranes prepared by filling quaternized polyphenylene ether with porous bacterial cellulose or functionalized bacterial cellulose as the substrate have better performance (especially ionic conductivity) than quaternized polyphenylene ether alkaline polyelectrolyte membranes.

[0077] Figures 3-7 Scanning electron microscope (SEM) images of the composite alkaline polyelectrolyte membranes prepared in Examples 1-5. Figure 3 and Figures 4-7 The comparison shows that functionalization of bacterial cellulose improves the compatibility between the porous substrate and the filler. The functionalization process of bacterial cellulose involves first coating the bacterial cellulose with a layer of polydopamine; then grafting polyethyleneimine onto this polydopamine layer, introducing a large number of primary and secondary amine groups. Next, through a ring-opening reaction between 2,3-epoxypropyltrimethylammonium chloride and the primary and secondary amine groups, the primary and secondary amine groups are converted into tertiary amine groups. Simultaneously, the quaternary ammonium groups on the 2,3-epoxypropyltrimethylammonium chloride are indirectly grafted onto the bacterial cellulose fibers. Furthermore, functionalized bacterial cellulose involves a series of physicochemical modifications to imbue the surface of the bacterial cellulose fibers with tertiary amine groups and quaternary ammonium groups. The tertiary amine groups can react with brominated polyphenylene ether to form quaternary ammonium groups, which indirectly connect the brominated polyphenylene ether and the bacterial cellulose, achieving a cross-linking effect. Therefore, functionalized bacterial cellulose, as a porous substrate filled with quaternized polyphenylene ether, improves the compatibility between the porous substrate and the filler.

[0078] Depend on Figures 4-7 The comparison shows that during the functionalization modification of bacterial cellulose, a specific amount of polyethyleneimine was found to significantly improve membrane performance.

[0079] Therefore, the bacterial cellulose / quaternized polyphenylene ether composite alkaline polyelectrolyte membrane and the functionalized bacterial cellulose / quaternized polyphenylene ether crosslinked composite alkaline polyelectrolyte membrane prepared by this invention have the potential to be used in anion exchange membrane fuel cells.

[0080] Membrane performance testing methods:

[0081] (1) The OH- ion conductivity of the membrane was tested under fully humid conditions using the AC impedance method on a Metrohm Autolab 302N frequency response analyzer, with a frequency scan range of 1–10. 6 The AC signal amplitude is 100mV at Hz. The cut membrane (2cm × 3cm) is placed on a self-made testing platform. The OH- ion conductivity σ (S / cm) of the membrane is calculated using the following formula:

[0082] σ=R / LA

[0083] In the formula, L and A are the distance between the two electrodes and the effective cross-sectional area of ​​the membrane under test between the two electrodes, respectively, and R is the impedance of the membrane, which is obtained through the Nyquist plot.

[0084] (2) Tensile strength: The membrane sample was cut into a rectangular strip with length × width = 40 × 10 mm. The tensile test was carried out on a Shimadzu AG-IC universal tensile tester at a stretching rate of 30 mm / min under room temperature conditions. The maximum tensile stress experienced by the membrane sample until it broke was recorded as the tensile strength.

Claims

1. A method for preparing a functionalized bacterial cellulose cross-linked composite alkaline polyelectrolyte membrane, characterized in that, Includes the following steps: (1) Purification of bacterial cellulose; (2-1) Quaternary ammonium-tertiary amine functionalization modification of purified bacterial cellulose: The purified bacterial cellulose obtained in step (1) was first immersed in a Tris buffer solution containing dopamine hydrochloride at pH 8 to 8.5, and after sonication, it was stirred for 12 to 24 hours. Then it was immersed in a Tris buffer solution containing polyethyleneimine, and after sonication, it was impregnated for 24 to 48 hours. Finally, it was immersed in a 2,3-epoxypropylammonium chloride solution, and after sonication, it was stirred at room temperature for 1 to 3 hours, and then treated at 70 to 80°C for 4 to 6 hours to obtain a functionalized bacterial cellulose porous substrate. (2-2) Dissolve brominated polyphenylene ether and impregnate it into the pores of the functionalized bacterial cellulose porous substrate obtained in (2-1). The brominated polyphenylene ether undergoes a cross-linking reaction with the functionalized bacterial cellulose porous substrate to obtain a polymer cross-linked functionalized bacterial cellulose membrane. (3) Quaternize the brominated polyphenylene ether solution that has been impregnated with the crosslinking residue in the polymer crosslinked functionalized bacterial cellulose membrane obtained in (2-2), impregnate and fill the bacterial cellulose, and then dry and ion exchange to obtain a functionalized bacterial cellulose crosslinked composite alkaline polyelectrolyte membrane.

2. The preparation method according to claim 1, characterized in that, The Tris buffer solution is an aqueous solution of 0.01~0.04 mol / L tris(hydroxymethyl)aminomethane; the mass concentration of dopamine hydrochloride is 1~5 g / L; and the mass concentration of polyethyleneimine is 2~12 g / L.

3. The preparation method according to claim 2, characterized in that, The mass concentration of the polyethyleneimine is 6~8 g / L.

4. The preparation method according to claim 3, characterized in that, The mass concentration of the polyethyleneimine is 8 g / L.

5. The preparation method according to claim 2, characterized in that, The mass concentration of 2,3-epoxypropylammonium chloride is 3~4 g / L.

6. The preparation method according to claim 5, characterized in that, The mass concentration of the 2,3-epoxypropylammonium chloride is 3.33 g / L.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The brominated polyphenylene ether is dissolved to form a brominated polyphenylene ether solution with a concentration of 1wt% to 5wt%, wherein the degree of bromine substitution of the brominated polyphenylene ether is 40% to 60%; the solvent for dissolving the brominated polyphenylene ether is selected from any one of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

8. The preparation method according to claim 7, characterized in that, The quaternizing agent is trimethylamine, and the quaternization time is 12~24h.

9. The preparation method according to claim 7, characterized in that, The time for impregnating and filling bacterial cellulose with brominated polyphenylene ether is 12~24h.

10. The preparation method according to claim 7, characterized in that, The steps for purifying bacterial cellulose membranes are as follows: Soak the bacterial cellulose membrane in deionized water for 12-48 h to allow it to fully absorb water, then remove it and soak it in 0.1-1 mol / L NaOH solution and heat it at 80-90℃ for 2-3 h. After cooling to room temperature, wash it repeatedly with a large amount of deionized water until it is neutral to obtain the purified bacterial cellulose membrane.

11. The preparation method according to claim 10, characterized in that, The bacterial cellulose has a diameter of 30~100 nm and a length of 10μm~50μm.

12. The preparation method according to claim 11, characterized in that, The bacterial cellulose has a diameter of 50-100 nm and a length of 10-20 μm.

13. The application of the functionalized bacterial cellulose crosslinked composite alkaline polyelectrolyte membrane prepared by any one of claims 1 to 12 in the preparation of anion exchange membrane fuel cells.

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